1. Field of the Invention
This invention relates to a stereoscopic microscope, for example, a microscope for ophthalmic operations or the like, and more particularly to a stereoscopic microscope provided with a second stereoscopic observation optical system for quickly and competently assisting an operator during an operation.
2.Description of the Prior Art
Stereoscopic microscopes are widely used for medical treatments such as operations and examination s and in research and medical industries. n operations, they are useful to improve the degree of precision and safety thereof.
Generally, when an operation is to be effected by the use of a microscope for operation, an assistant assists an operator while observing the patient from beside the operator. Therefore, it is necessary for the assistant to constantly stereoscopically observe the same affected part that the operator observes. However, with the conventional stereoscopic microscope of this type, it is often the case that an observation optical system for the assistant from the operator's direction of observation or stereoscopic observation is impossible. With the device disclosed in the Japanese Utility Model Publication No. 39364/1980 which eliminates this problem, the assistant can obtain stereoscopic observation substantially similar to what the operator has. In this case, however, the assistant can only position himself in a predetermined direction relative to the operator and the assistant's range of movability is limited. Improving this limitation of the range of movability has been proposed, but the achieved range of movability is not yet satisfactory.
FIG. 1 of the accompanying drawings shows an optical system of a microscope for operation according to the prior art. The affected part E is stereoscopically observed by the operator from two eyepieces 4a and 4b through an objective 1, two sets of zoom lenses 2a and 2b and beam splitters 3a and 3b. On the other hand, the assistant observes the affected part E from a direction L' entirely different from the operator's direction of observation between the affected part E and the objective 1, or observes the affected part E from one direction L of the left and right observation systems through the beam splitter 3b while separating the light beam.
FIG. 2 of the accompanying drawings shows another example of the prior art in which the assistant also can effect stereoscopic observation. The use areas A in the objective 1 of an observation optical system for operator and the use areas Aa of an observation optical system for an assistant are fixed at positions forming an angle of 90.degree. with each other, as viewed from the direction of the optic axis O of the objective 1. Thus, in these examples of the prior art shown in FIGS. 1 and 2, there arises a problem that the assistant's position cannot be changed.
FIG. 3 of the accompanying drawings shows an example of the prior art proposed to overcome the above-noted disadvantage. In this example, as in the case of FIG. 1, the affected part E is observed by the operator through an objective 1, two sets of zoom lenses 2a and 2b, beam splitters 3a and 3b and eyepieces 4a and 4b. On the other hand, the assistant observes the affected part E through the objective 1, zoom lenses 2a' and 2b', mirrors 5a and 5b and eyepieces 4a' and 4b', (2b', 5band 4b' being not shown), and the use areas Aa in the objective 1 of this observation optical system for assistant are rotatable relative to the optical system for operator, as shown in FIG. 4 of the accompanying drawings. That is, in FIG. 4, relative to the use areas A of the observation optical system for operator, the pair of use ranges Aa and Aa for left and right eyes of the observation optical system for assistant are rotated about the optic axis O of the objective 1.
This example of the prior art, as compared with the two previous examples, is remarkably improved from the viewpoint of the degree of freedom of the assistant's position, but the use areas A and Aa of the two observation optical systems are installed for rotation in the same space and therefore, the range of rotation of the areas Aa relative to the areas A is also limited. Particularly, with microscopic operations in cerebral surgery, it is often the case that the innermost part of a deep hole is observed, and the distance d between the pair of optical systems in FIG. 3 cannot be selected to value greater than necessary and therefore, the range of rotation of the use areas Aa is limited. Also, in recent years, particularly, microscopes which enables objects to be seen brightly and well have been desired with the advanced degree of precision of operations or the like and therefore, it is inappropriate to make the diameter of the zoom lenses 2a and 2b smaller, and this also leads to a disadvantage that the range of rotation of the use areas Aa is limited.